Fabrication of hollow articles



Dec. 4, 1962 U. R. .JAEGER 3,066,389

FABRICATION OF HOLLOW ARTICLES Filed July 30, 1956 2 Sheets-Sheet l FIGB.

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Dec. 4, 1962 U, R. JAEGER 3,066,389

FABRICATION OF' HOLLOW ARTICLES Filed July 30, 1956 2 Sheets-Sheet 2 L (ze 697 (57 g F IG .7.

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This invention relates to the fabrication of hollow articles and more specifically to forming the hollows in such articles.

In the fabrication of hollow sheet metal panels by one well known process, two sheets of metal are arranged 1n stack-like fashion with a design of weld-inhibiting material applied to a portion of one of the adjacent faces of the sheets. The sheets are secured together to prevent relative slippage and are then welded together in their adjacent areas not separated by the weld-inhibiting material, in any suitable manner, such as 'by hot rolling. As the sheets are being welded together by hot rolling, they are elongated in the direction of rolling and therefore the design of weld-inhibiting material must be foreshortened in the intended direction of rolling when it is applied to the sheet. After the sheets are welded together they are usually softened as by annealing and the unjoined portion to which the weld-inhibiting material has been applied is outwardly expanded, as by injecting therein a uid pressure of sufficient magnitude to permanently dstend the sheets in the area adjacent to the weld-inhibiting design. r`fhe weld-inhibiting design may assume any desired configuration, for example, a design which will define, after expansion of the blank, a fluid conveying circuit of the type required in refrigerator heat exhanger panels. The aforementioned process is more fully described in U.S. Patent 2,690,002, issued September 28, 1954.

This invention comprehends expanding an integral blank having an unjoined interior portion, by positioning the blank between a pair of spaced-apart hard pressure pads with a compressible pressure pad inserted between a portion of the unjoined area of the blank and one of the hard pressure pads, or preferably a compressible pad next to the blank and a hard shim between the compressible pad and the hard pressure pad, and then expanding the blank by injecting into the unjoined portion thereof a iiuid pressure of sufficient magnitude to permanently distend the blank into rm engagement with the spacedapart hard platens. The hard pressure pads are spaced apart a distance such that upon expansion of the unjoined portion of the biank the resultant distended portions firmly engage the hard pressure pads and the portions of the distentions which engage the hard pressure pads are thereby flattened. The resultant distentions on the por* tion of the side of the blank in engagement with the cornpressible pressure pad are impressed into the compressible pressure pad. The compressible pressure pad tends to hold the side of the blank opposite thereto firmly against the hard pressure pad, limiting outward distention of the unjoined portion of the blank on the side opposite the compressible pressure pad so that this side is substantially smooth.

As used herein, the term smooth means a surface devoid of depressions or protrusions in the overall general configuration of the surface.

This invention is directed primarily to the expansion of metal panels from blanks fabricated with an unjoined interior portion, but the invention is equally applicable to similar panels fabricated from materials other than metal, such as various plastics, and to panels fabricated from dissimilar materials such as metal and a plastic joined together with an unjoined portion between the sheets.

It is an object of this invention to fabricate a hollow hiid@ Patented Bec. 4i, ES

panel in` which a portion of one side is substantially smooth and the remaining portion of this Side and other side is distended to a greater degree than the substantially smooth portion.

Another object of this invention is to provide a method of fabricating panels of the type described in the aforementioned patent, U.S. 2,690,002, in which a portion of one of the outer surfaces is substantially smooth in the areas adjacent an unjoined interior area of said panel.

Additional objects and advantages will. be apparent from the following description and drawings in which:

FIGURES l and 2 indicate schematically a process for fabricating a blank from which a hollow smooth-sided panel is subsequently formed, and more specifically;

FIGURE l is a perspective view of a sheet of material having applied to the surface thereof a pattern of weldinhibiting material;

FIGURE 2 is a perspective View of the sheet shown in FIGURE l with a second sheet superimposed thereon in laminar fashion and tacked thereto as by spot welding, with the pattern of weld-inhibiting material sandwiched between the sheets and showing the sheets being welded together in a rolling mill to form a blank;

FIGURE 3 is a longitudinal sectional schematic view of the resultant blank of FIGURE 2, the line 3 3 in FIGURE l indicating the portion of the Weld-inhibiting pattern shown in FIGURE 3, and showing the blank positioned between a pair of pressure pads;

FEGURE 4 is a transverse sectional view of the mechanism shown in FIGURE 3 after the pressure pads have been properly spaced apart and the unjoined portion of the lblank expanded, the section of the panel being indicated 'by the line 4 4 in FIGURE 6 of the finished panel;

FIGURE 5 is a sectional view of another position of the finished panel taken on the line 5 5 in FGURE 6;

FIGURE 6 is a perspective View of one side of the expanded panel, and;

FIGURE 7 is a perspective view of the opposite side of the expanded panel, shown in FGURE 5,

Referring to the drawings, a sheet l such as aluminum or copper has applied to a clean surface 3 thereof a design S of weld-inhibiting material. The weld-inhibiting design 5 includes a pair of header areas 7 interconnected by conduit strips 9. The strips 9 have a wider weld-inhibiting portion l1 at their midportion for a purpose to be described hereinafter. The weld-inhibiting design S includes a strip i3 interconnecting a portion of the aforementioned design with an edge I5 of the sheet 1. In this instance, the strip i3 interconnects an edge f5 of the sheet and one of the header areas 7. A second sheet I7 is superimposed on the surface 3 of the first sheet l. The two sheets are then tacked together as by spot welding i9 to prevent relative slippage of the adjacent surfaces of the sheets during a subsequent welding operation. After the sheets have been tacked together they are welded together along their adjacent surfaces not separated by the weld-inhibiting material 5'. One well known method of welding the sheets together is by hot rolling, in which the sheets are first heated and then passed through mill rolls 21, between which they are reduced in thickness and elongated in the direction of rolling. If desired, the resultant blank 23 having an unjoined interior portion 25 may be softened in any appropriate manner as by annealing and thereafter' the blank may be cold rolled to provide a more even thickness and again annealed. The inlet design 13 of weld-inhibiting material produces an unjoined inlet 27 into the unjoined header and conduit design after welding the sheets together to form a blank.

Referring to FIGURE 3, a compressible pressure pad 29 is positioned on the top surface of the blank 23 and a hard shim 30 is positioned on top of the pad 29. The

accesso blank, compressible pressure pad, and shim are positioned between a pair of hard pressure pads 3l, and a fluid pressure conveying nozzle is inserted into the inlet 27 in the blank. The hard pressure pads 3l are respectively secured to a fixed jaw 33 and a vertically movable jaw 35 of a press 337. The movable upper jaw 35 of the press is secured to a plunger 3@ received in a cylinder di with a fluid-tight sliding lit. The movable jaw 35 is maintained in a raised position in any appropriate manner as by a spring 43 engaging a shoulder 45 on the lower end of the cylinder il and a shoulder L37 on the plunger 39. The cylinder dl is fixed with respect to the lower jaw 33 of the press in any appropriate manner as by arms 49. A fluid pressure conveying conduit l opens into the upper end of the cylinder di for injecting a iiuid into the cylinder thereby forcing the plunger 39 downward the hard upper pressure pad toward the hard lower pressure pad and shim. The hard pressure pads 3l are spaced from each other as shown in FEGURE 4. The spacing may be adjusted as by shims 5d and the spacing is such that the upper hard pressure pad does not engage the blank 23. However, the compressible pressure pad 29 and shim 30 are clamped between the blank 23 and hard upper pressure pad 3l. The unjoined portion 2.5 of the blank 23 is then expanded by injecting fluid pressure therein through the nozzle 32 and conduit S5 connected thereto.

The compressible pressure pad 29 is preferably of a resilient material such as sponge rubber, but any type of rubber-like material is suitable. The pad 29 may be of a nonresilient material such as balsa wood, but unless the pad is resiiient, it will not return to its original condition. The hard shim 3@ is not mandatory, but it has been found that a more nearly smooth portion will be obtained if such a shim is used. The softness or compressibility and thickness of the pressure 'pad 29, the thickness of the shim 30, the thickness of each side of the unjoined portion of the blank 2.3, the strength and other characteristics of the 'sheets l and 17 from which the blank 23 is fabricated, and the expansion pressure injected through the nozzle 32 into the unjoined portion of the blank all affect the resultant degree of smoothness.

For example, a blank fabricated from ll00 or 2S Aluminurn sheets, both .126 inch thick prior to being passed through mill rolls and welded together, and having a tensile strength of about 13,000 p.s.i. when fully annealed, after having been welded together to form a blank .060 inch thick having an unjoined interior portion forming a con duit pattern with each conduit approximately 3A; inch thick in the area to be inflated so as to provide substantially smooth surfaces when expanded against a quarter inch thick rnedium grade soft block stock industrial sponge `rubber pad having a density of about 2l pounds per cubic foot, a compressibility of 2 to 5 pounds per square inch to compress the pad to 75% of its original thickness, and a minimum elongation of 250% backed up by a hard shim .030 inch thick, all positioned between hard pressure pads spaced apart .180 inch and expanded by a pressure of 3,000 p.s.i. exerted within the unjoined portion of the blank, produced a hollow panel having an overall outside tube height of .180 inch thick in the area away from the rubber pad, land an overall tube height of approximately .130 inch in the area covered by the rubber pad, with a resultant tube height on the substantially smooth side of between approximately .015 and .020 inch.

The compressible pad may be of solid rubber having similar physical characteristics as the previously described sponge rubber to prevent the compressibility of the pad from being affected by liquid spilled thereon.

The harder the compressible pressure pad or the greater the shim thickness, the flatter will be the resultant panel in the area of the compressible pad and the smaller the cross-sectional area of the expanded portion. A shim is therefore not mandatory, but is preferred because a flatter panel is thereby produced. Since the total outward disl tention of the expanded portion of the panel in the area of the substantially smooth side is less than the remainder of the expanded portion, the unjoined portion may be wider adjacent the smooth area as indicated by the design of the weld-inhibiting material 11.

FXGURES 6 and 7 show opposite `sides of the expanded panel 6l. In FIGURE 6 the conduits d3 each have a wider portion 65 in the area which engages the compressible pressure pad 29; The wider portion 65 of the conduits corresponds to the wider portion il of the weld-inhibiting pattern shown in FiGURE l. The conduits 63 have iiat outer surfaces through engagement with the hard pressure pads 3l. With reference to FIGURE 5, it will be seen that the outer portions 67 distend outwardly to a greater extent than did the wide conduit portion 65. Therefore, in order to assure an adequate cross-sectional area of the conduits 65, this portion should be wider than the end portions 67, and therefore the weld-inhibiting d-esign shown in FIGURE l has a wider midportion l1. The rever-se side of the panel is shown in FIGURE 7, and it will be noted that the wide portion 65 of the conduits 63 is distended outwardly very slightly and that the midportion of the panel 61 is substantially smooth. During the expansion of the blank, the pressure of the compresl sible pressure pad 29 causes the adjacent portion of the opposite side of the blank to be firmly held against the lower hard pressure pad 31 so that as the conduits 67 distend outwardly on both sides of the blank 23, and the midportion of the blank becomes stepped as indicated at 69.

After expansion of the unjoined portion 25 of the blank 23 to form hollow portion 59 of the panel 6l, it may be necessary to control the release of the expansion pressure within the hollow portion 59 and the pressure of a resilient pressure pad 29 against the distended portion of the panel 6l, in order to prevent rupturing the panel through the force of the expansion uid and to prevent collapsing the extended hollow portion 59 of the panel through the force of the resilient pressure pad. By releasing the pressure in cylinder 41 concurrently with the pressure in the hollow portion S9 of the panel, yany tendency of the pad to collapse the hollow portion or for the expansion pressure to rupture the hollow portion of the panel is retarded.

Although the invention has been described with reference to particular embodiments, materials, and details7 various modifications and changes Will be apparent to one skilled in the art, and the invention is therefore not to be limited to such embodiments, materials or details except as set forth in the appended claims.

I claim:

l. In the method of fabricating a hollow article from a blank having an unjoined interior portion contained within opposite outer faces of said blank by expansion of said unjoined interior portion with uid pressure wherein said unjoined interior portion comprises at least two Inajor component portions disposed different corresponding sections of said blank and interconnected to each other and with said blank disposed between a pair of opposed rigid pressure pads adjacent to corresponding portions of said outer faces of said blank at least in areas of said faces opposite said component portions, the improvement comprising interposing a compressible pressure pad between one of said faces and the rigid pad adjacent said one face in the area of said blank opposite one of said component portions with said rigid pads spaced from each other a distance equal to the amount of expansion desired in other component portions upon subsequent expansion of said blank by fluid pressure and with said compressible pad having a degree of compressibility permitting expansion of the area of said one face opposite said one component portion into said compressible pad an yamount substantially greater than the corresponding area of the other of said opposite faces opposite said one component portion; injecting into said unjoined interior portion said fluid pressure of sufficient magnitude to expand and impress said one component portion into said compressible pad while simultaneously expanding said other component portions against said rigid pads; and concurrently releasing the pressure exerted by said compressible pad on said blank and said fluid pressure while maintaining a relationship between them sufficient to, both, prevent collapse of said one component portion by the pressure of said compressible pad and to prevent rupturing of said one component portion by the iiuid pressure within said unjoined interior portion.

2. The method of `claim 1 wherein said unjoined interior portion comprises at least three major component portions disposed in diierent corresponding sections of said blank with said one component portion positioned between at least two of the remaining component portions of said unjoined interior portion.

3. In the method of fabricating a hollow article from a blank having an unjoined interior portion contained within opposite faces of said blank by expansion of said unjoined interior portion with fluid pressure with L said blank disposed between a pair of opposed rigid pressure pads adjacent to said outer faces of said blank at least in the `area of said faces opposite said unjoined interior portion wherein said unjoined interior portion comprises at least two major component portions disposed in different corresponding sections of said blank and interconnected to each other, the improvement comprising interposing a compressible pressure pad between one of said faces and the rigid pad adjacent said one face in the area of said blank opposite one of said component portions; closing said rigid pads to reduce the spacing between them equal to the amount of expansion desired in remaining component portions with said compressible pad having a degree of compressibility permitting expansion of said one face opposite said one component portion into said compressible pad an amount substantially greater than the corresponding area of the opposite face of said 'blank opposite said one component portion; injecting into said unjoined interior portion said fluid pressure of suflicient magnitude to expand and impress said one component portion into said compressible pad while simultaneously expanding said remaining component portions against said rigid pads; and concurrently releasing the pressure exerted by said compressible pad on said blank and said uid pressure while maintaining a relationship between them sufficient to, both, prevent collapse of said one component portion by the pressure of said compressible pad and to prevent rupturng of said one component portion by the fluid pressure within said unjoined interior portion.

4. The method of claim 3 wherein said unjoined interior portion comprises at least three major component portions disposed in different corresponding sections of said blank with said one component portion positioned between at least two of the remaining component portions of said unjoined interior portion.

5. In the method of fabricating a hollow article from a blank having an unjoined interior portion contained within opposite outer faces of said blank by expansion of said unjoined interior portion with fluid pressure wherein said unjoined interior portion comprises at least two major component portions disposed in different corresponding sections of said blank and interconnected to each other and with said blank disposed between a pair of opposed rigid pads adjacent to corresponding portions of said outer faces opposite said component portions with said pads spaced from each other a distance equal to the amount of expansion desired in said unjoined interior portion upon subsequent expansion of said blank by fluid pressure, the improvement comprising interposing a compressible pressure pad between one of said outer faces and the rigid pad adjacent said one face in the area thereof opposite one of said component portions with said compressible pad having a degree of compressibility permitting the expansion of said one face adjacent and opposite said compressible pad to an amount substantially greater than the corresponding area of the opposite face of said blank; injecting into said unjoined interior portion said fluid pressure of sutcient magnitude to expand and impress said one component portion into said compressible pad While simultaneously expanding remaining component portions against said rigid pads, and concurrently releasing the restraining pressure exerted by said compressible pad on said blank and said Huid pressure while maintaining -a relationship between them sufficient to, both, prevent collapse of said one component portion by the pressure of said compressible pad and to prevent rupturing of said component portion by the iiuid pressure within said unjoined interior portion.

References Cited in the file of this patent UNITED STATES PATENTS 2,479,702 Rood Aug. 23, 1949 2,582,358 Schoellerman Jan. 15, 1952 2,662,273 Long Dec. 15, 1953 2,690,002 Grenell Sept. 28, 1954 2,728,317 Clevenger et al. Dec. 27, 1955 2,749,867 Engel .Tune 12, 1956 2,822,194 Fentress Feb. 4, 1958 2,866,429 Staples Dec. 30, 1958 

